What happened
On the afternoon of 23 November 2023, a Robinson R44 Raven II helicopter, registration ZS-PSZ, was conducting a private flight departing from Ultimate Heli in Midrand, Gauteng. The flight, operated under Part 91 regulations, was intended to be a short trip returning to the same helipad. After taking off and navigating toward Grand Central Airport, the aircraft turned south toward the general flying area.
While cruising at 5,300 feet, the engine suddenly stopped without any prior warning. The pilot immediately attempted an autorotation to manage the descent. However, the aircraft entered an uncontrolled descent and struck the ground hard on its skid landing gears in an open field approximately 1.5 nautical miles south of the departure point. The impact destroyed the aircraft. The pilot sustained serious injuries, while the second occupant on board escaped without injury.
The investigation
SACAA AIID investigators examined the wreckage and the engine components to identify the source of the power loss. Post-accident inspections of the fuel, ignition, and induction systems revealed no abnormalities. The fuel tanks contained the correct grade of Avgas 100LL and were free of contaminants. Furthermore, the engine was later tested at an approved facility, where it demonstrated the ability to operate at full power without any detectable defects.
Technical logs showed that the helicopter had undergone a 100-hour mandatory periodic inspection only 16.1 airframe hours prior to the accident. The investigation also focused on the flight dynamics during the emergency, noting that the collective pitch control lever was found in the "UP" position following the crash.
Findings
- The engine stoppage was undetermined, as no mechanical or fuel-related defects were found during the post-crash examination.
- The helicopter utilizes a low-inertia rotor system, which is highly susceptible to rapid decay in main rotor RPM (Nr) once engine power is lost.
- The position of the collective pitch control lever suggests a delayed lowering of the collective pitch, which likely caused the main rotor to stall and rendered a safe landing impossible.